This disclosure relates generally to the field of semiconductor manufacturing and more specifically, to the use of a developing bottom antireflective coating placed between two photoresist layers to achieve a packing and unpacking process for forming openings in a device substrate.
A packed-and-unpacked process generally combines a packed contact hole pattern photomask and an unpacked contact hole pattern photomask to produce a quality pattern with well-defined critical dimensions in a photoresist layer and on an etched substrate. The packed pattern is a combination of desired contact openings and also undesired contact openings that are added to densify the first photomask. The packed pattern photomask is utilized to expose and develop the combined pattern of desired and undesired contact openings in a first layer of photoresist. There are two variations that allow the unpacked pattern to achieve the selection of desired contact openings into the final photoresist pattern. The first variation defines islands in the second photoresist layer that are slightly larger than the undesired contact openings in the first photoresist layer and therefore securely cover them. These photoresist islands in the second photoresist layer, in the first variation, are based on the undesired contact openings in the first photoresist layer. The second variation defines larger areas in the second photoresist layer that cover not only the undesired openings in the first photoresist layer, but also the broader areas between the desired contact openings. The remaining openings in the second photoresist layer, over the desired contact openings in the first photoresist layer, are slightly larger than those desired contact openings in the first photoresist layer. The remaining openings in the second photoresist layer, in the second variation, are based on the desired contact openings in the first photoresist layer.
Photoresists are photosensitive films used for the transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced transformation of the photoresist coating thereby transferring the pattern of the photomask to the photoresist-coated substrate. Following the exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or crosslink in a reaction between a photoactive compound and polymerizable reagents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For a positive-acting photoresist, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less soluble. In general, photoresist compositions comprise at least a resin binder component and a photoactive agent.
In the production of semiconductor devices, an integrated circuit substrate is coated with a film of photo-patterning resist or photoresist, which is exposed to actinic radiation, and developed to define a resist image over the integrated circuit substrate. The resist image includes both lines and spaces, wherein portions of the photo-patterning resist that are removed from the spaces and the portions that remain form the lines. Resolution of the image transferred to the substrate is dependent on the resolution of the resist image.
Typically, these submicrometer closely spaced lines are formed on substrates having non-planar surfaces and other irregular structures. These rough or irregular topographies make it difficult to use a single layer of photoresist without having distorted images. These distorted images can result from the scattered radiation from the underlying structures during the exposure of the photoresist layer. To prevent reflection of actinic radiation into a photo-patterning resist, one or more layers of antireflective coating (ARC) may be provided between a substrate and a photo-patterning resist film.
What is needed is an improved method for using ARC to achieve a packed-and-unpacked process.